Television picture tubes having an electron gun with aperture electrode shielding means

Abstract

This disclosure depicts a television cathode ray picture tube having a plural-beam electron gun for projecting in superimposition on the picture imaging screen of the tube at least two electron beam spots. The gun includes at least one aperture electrode having an aperture for passage therethrough of each of said beams. The beams are subject to a first-order aberration attributable to the aperture electrode resulting in the astigmatizing, and consequent distortion of, the beam spots. This astigmatizing is due to the coalescing of electric field vectors contiguous to each aperture with the vectors of at least one adjacent aperture. The improvement comprises shielding means interposed between the apertures comprising wall means. The wall means are effective to mutually shield the apertures and isolate the electric field vectors to ameliorate the first order aberration. The wall means introduces, however, higher-order aberrations due to a disordering of the electric field vectors resulting in forms of beam spot distortion other than astigmatic. The improvement further comprises a configuration of the wall means wherein a section of the wall means comprises a cut-out. The cut-out is shaped so as to be effective to re-order the vectors and ameliorate the effect of the higher order aberrations. As a result, the electron gun having aperture electrodes is enabled to project substantially undistorted beam spots.

I claim: 
     
       1. In a television cathode ray picture tube having a plural-beam electron gun for projecting in superimposition on the picture imaging screen of said tube at least two electron beam spot, said gun including at least one aperture electrode having an aperture for passage therethrough of each of said beams, said beams being subject to a first-order aberration attributable to said aperture electrode resulting in the astigmatizing and consequent distortion of said beam spots due to the coalescing of electric field vectors contiguous to each aperture with the electric field vectors of at least one adjacent aperture, an improvement comprising shielding means interposed between said apertures comprising wall means, said wall means being effective to mutually shield said apertures and isolate said electric field vectors to ameliorate said first-order aberration, said wall means introducing, however, higher-order aberrations due to a disordering of said electric field vectors resulting in forms of beam spot distortion other than astigmatic, said improvement further comprising a configuration of said wall means wherein a section of said wall means comprises an in-curving cut-out comprising at least a third of the area of said wall means, said cut-out being symmetrical about a plane defined by the axes of said apertures and so configured that there is greater shielding off-plane than on-plane, said cut-out being effective to re-order said electric field vectors and ameliorate the effect of said higher-order aberrations whereby said gun is enabled to project substantially undistorted beam spots. 
     
     
       2. In a television cathode ray picture tube having a three-beam unitized, in-line electron gun for projecting in superimposition on the picture imaging screen of said tube three electron beam spots, said gun including at least one aperture electrode having three apertures for passage therethrough of said beams, said electron gun including focus lens means comprising at least three electrodes for establishing a single, continuous electrostatic focusing field characterized by having an axial potential distribution which, at all times during tube operation, decreases smoothly and monotonically from a relatively intermediate potential to a relatively low potential spatially located at a lens intermediate position, and then increases smoothly, directly and monotonically from said relatively low potential to a relatively high potential, said beams of said gun being subject to a first-order aberration attributable to said aperture electrode resulting in the astigmatizing and consequent distortion of said beam spots due to the coalescing of electric field vectors contiguous to each aperture with the electric field vectors of at least one adjacent aperture, an improvement comprising shielding means interposed between said apertures comprising wall means, said wall means being effective to mutually shield said apertures and isolate said electric field vectors to ameliorate said first-order aberration, said wall means introducing, however, higher-order aberrations due to a disordering of said electric field vectors resulting in forms of beam spot distortion other than astigmatic, said improvement further comprising a configuration of said wall means wherein a section of said wall means comprises an in-curving cut-out comprising at least a third of the area of said wall means, said cut-out being symmetrical about a plane defined by the axis of said aperture and so configured that there is greater shielding off-plane than on-plane, said cut-out being effective to re-order said electric field vectors and ameliorate the effect of said higher-order aberrations whereby said gun is enabled to project substantially undistorted beam spots. 
     
     
       3. In a television cathode ray picture tube having a plural-beam electron gun for projecting in superimposition on the picture imaging screen of said tube at least two electron beam spots, said gun including at least one aperture electrode having an aperture for passage therethrough of each of said beams, said beams being subject to a first-order aberration attributable to said aperture electrode resulting in the astigmatizing and consequent distortion of said beam spots due o the coalescing of electric field vectors contiguous to each aperture with the electric field vectors of at least one adjacent aperture, an improvement comprising shielding means interposed between said apertures comprising wall means, said wall means being effective to mutually shield said apertures and isolate said electric field vectors to ameliorate said first-order aberration, said wall means introducing, however, higher-order aberrations due to a disordering of said electric field vectors resulting in forms of beam spot distortion other than astigmatic, said improvement further comprising a configuration of said wall means wherein a section of said wall means comprises a cut-out, said cut-out being symmetrical about a plane defined by the axes of said apertures and so configured that there is greater shielding off-plane than on-plane, said cut-out being effective to reorder said electric field vectors and ameliorate the effect of said higher-order aberrations whereby said gun is enabled to project substantially undistorted beam spots.